GenericJavaScanner

Scans a merged Java resource pack directory for 1.21.4+ items definition files across every namespace, including minecraft. Modern vanilla item overrides such as assets/minecraft/items/carrot_on_a_stick.json are where many packs define their custom-model-data branches. All plugin namespaces are processed uniformly; there is no FMM-specific carve-out. A producer can leave items out of the conversion by declaring them Java-only, see JAVA_ONLY_DIR.

This is the entry point of the generic Java→Bedrock pipeline. Subsequent phases (model walker, base-item resolver, geometry/attachable emission) consume the ItemsDefinition list produced here.

Phase 1 scope: discovery only. Files are parsed into ItemsDefinition records but no conversion is performed.